The character of Mitch is created to be juxtaposed to the character of Blanche. They are meant to be complete opposites, whose only common trait is that they both possess ulterior motives in their admiration and want of each other.
Mitch is characterized as a "simpleton". He is simple-minded, and not intellectually gifted. His personality is not charming; he is actually awkward with very little sense on how to treat women (this is due to inexperience).
Additionally, he seems to have an Oedipus complex. His mother, who is sick at the time he meets Blanche, is the center of his life and her opinion matters to him a lot. Perhaps this same dependence of his mother is what makes him overlook the fact that Blanche is older than him; he actually finds an attraction in this.
As far as language choices, Mitch is supposed to appear at a much lower intellectual level than Blanche. This is why it is Blanche who carries out most of the dialogue between the two, leaving him no other choice but to merely respond in short.
However, all of these character traits fit perfectly with Blanche's agenda: she is quite aware about Mitch's lower attainments, about his naivete, and about his lacklustre life. Yet, at this point, Blanche is no longer pursuing the money, adventure, nor prestige of the past; she is desperate now: she will take whatever she can get as long as she can get out of her current situation.
“I want to rest! I want to breathe quietly again! Yes—I want Mitch…very badly! Just think! If it happens! I can leave here and not be anyone’s problem…”
Therefore, Mitch would have been a perfect escape route for Blanche had it not been for Stanley's intrusion on behalf of his friend.
- Whenever Blanche wanted to conceal her age, Mitch was fine with covering the lights with Chinese lanterns.
- Whenever Blanche pretended to be chaste and would reject Mitch's approaches to kiss her, Mitch truly believed her.
- Whenever Blanche would tell a story, whether true or false, Mitch would respond by telling her a bit about himself. It was a perfect courtship where two people who were lonely admit to need each other's company.
Even Mitch admits to as much:
You need somebody. And I need somebody, too. Could it be — you and me, Blanche?”
Basically Mitch and Blanche were perfect for each other for what they needed at the time. Since Mitch is so simple and easily led (both by Blanche as well as by Stanley), his character is the perfect one to fall for Blanche's way. Sadly for Blanche, Mitch was carefully warned against Blanche and he was able to get away before it was too late.